亚波长介质光栅-金属Ag薄膜-周期性光子晶体混合结构的Fano共振传感机理

基于表面等离子体极化激元的传输特性和周期性光子晶体的光学特性,提出了一种在亚波长介质光栅-金属Ag薄膜结构中产生离散态,在周期性光子晶体结构中产生连续态的亚波长介质光栅-金属Ag薄膜-周期性光子晶体混合结构。通过对该结构进行理论分析和传输特性研究,阐述了该结构中Fano共振产生的机理,建立了基于角度调制的Fano共振传感结构模型,并定量分析了结构参数对反射光谱曲线的影响。结果表明:当周期性光子晶体周期层数N=4、光栅周期Λ=258 nm和金属Ag薄膜厚度d0=27 nm时,该结构的品质因数FOM值高达2.11×10^4,角灵敏度S=40(°)/RIU。该结构为亚波长介质光栅结构中实现Fano共振提供了有效的理论参考,对光学折射率传感结构的设计具有一定的指导意义。

Fano-Resonance Sensing Mechanism of Sub-Wavelength Dielectric Grating-Metal Ag Thin Film-Periodic Photonic Crystal Hybrid Structure

Based on the transmission characteristics of surface plasmon polaritons and the optical properties of periodic photonic crystals,a hybrid structure of sub-wavelength dielectric grating-metal Ag thin film-periodic photonic crystal is proposed,which produces discrete state in sub-wavelength dielectric grating-metal Ag thin film structure and continuous state in periodic photonic crystal structure.Through the theoretical analysis and transmission characteristics of the structure,the generation mechanism of Fano resonance in the structure is expounded,the Fano-resonance sensing structure model based on angle modulation is established,and the influence of the structural parameters on the reflection spectrum curve is quantitatively analyzed.Results show that when the periodic photonic crystal periodic layer number is N=4,the grating period isΛ=258 nm,and the Ag-film thickness is d0=27 nm,the quality factor FOM value of the structure can be as high as 2.11×10^4,and the angular sensitivity is S=40(°)/RIU.The proposed structure provides an effective theoretical reference for achieving Fano resonance in a sub-wavelength dielectric grating structure,and it has certain guiding significance to the design of the optical refractive index sensing structure.